Advanced Patient Assessment Practice Exam

Why is the electrical signal delayed slightly at the AV node?

1. To allow better filling of the ventricles

2. To protect the ventricles against excessively rapid atrial rates

3. To provide time for atrial contraction prior to ventricular systole

4. To prevent premature atrial beats from reaching the ventricles

The correct answer is: To prevent premature atrial beats from reaching the ventricles

The delay of the electrical signal at the AV node is primarily to provide a mechanism for better coordination between the heart's chambers. While options such as allowing ventricles to fill more effectively and protecting against rapid atrial rates are valid considerations in the overall function of the heart, the essence of the delay lies in facilitating the timing between arterial contraction and ventricular contraction. The AV node's delay allows for a period in which the atria can fully contract, ensuring that blood is effectively pushed into the ventricles before they contract. This synchronization is essential for maintaining optimal cardiac output. The delay also serves as a safeguard against excessively rapid rates of atrial contractions, which could lead to inefficient filling or ineffective pumping. It prevents premature atrial beats from reaching the ventricles by acting as a filter; this is critical in maintaining a stable rhythm and ensuring that the heart can function efficiently without being overwhelmed. Thus, the slight delay at the AV node is fundamentally tied to the overall physiology of the cardiac cycle, emphasizing the importance of timing and coordination in cardiac performance.